Method for preparing dicyclopentadienyl magnesium



0ct. 8 1968 DAVEY ET AL METHOD FOR PREPARNG DCYCLOPENTADENYL MAGNESUM Fi1ed june 16 1965 United SteS Ptent ABSTRACT 0F THE DISCLOSURE The invention is directed t0 an improvement in a method for preparing magnesium dicyclopentadieny1 vvherein cyc0pentadiene is reacted at an elevated telTlerature with Inagnesium to form magnesium dicycpentadienyl, the impr0vernent comprising bringing cycl0- entadiene in contact with a Inolten alloy containing about 35 veight percent of Inagnesium and about 6S Weight percent of lead at Said elevated temperature at a Selected P0int Within a cOnned reaction Zone vvhile causing the molten alloy t0 n10ve along an endless path passing through said p0int, a portion ()f Said path extending up- Wardly fr0m said 0int This invention contelnplates a novel method for the preparation of a meta1dicyc10pentadieny, Such as dicyc10pentadieny1magnesium, and an apparatus for use in the preparation of such c0mp0unds The United states patent t0 Winiam A. Barber, NO Z 788,377, describes a method for preparing dicyc10- pentadieny1 by reacting cyc10pentadiene with solid mag IesilllT, Such as magnesiun1 turnings, at a tenperature between about 40 and about 600 0T higher vve found that in the ractice of thiS Inethod carbon or Inagnesium carbide or magnesiun1 acetylide collects on the metal surface, and eventually reaction ceases.

In accordance vvith the present invention cyc10penta diene is introduced int0 a b0dy 0f a molten nagnesilIn alloy at a point a Substantial distance below the Surface 0f the m01ten alloy Whereby the cyc10pentadiene Teacts vvith the 1Tlagnesiun1 in the molten alloy to f0rm hydrogen and gaseous dicyc10pentadieny1, Which separate from the n...)1ten alloy at its surface and are caused t0 pass into a condenser, Where the dicyc10pentadieny1 is condensed to a liquid or Solid' Any Solid by-products of the Teaction are carried out of the Zone 0f reaction to the surface Of the molten alloy by upwardly flovving gas Stream The temperature of the n10lten al10y iS maintained between about 40 and about 600 C. but a temperature aS high aS 1000 C may be used. We have found a tem perature between about j40 C and about SSS C particularly suitable. Solid Inagnesium metal may be added fr0m time t0 time to replace the magnesium consuIned by the reaction.

In the practice 0f the invention vve prefer to emp10y an alloy of magnesium and lead. II()vvever, the lead nlay be replaced by other metals Which form sumciently 10W' Inelting binary alloys vvith magnesium, Such as aluminum, Silver, bismuth, calcium, cadmiun, Copper, galliufn, Inercury, Ilickel, tin, thalliuIn or zinc. Ternary alloys containing these and other metals also may be used. The preferred alloy contains about 35 Weight percent of magnesium and about 6 Weight percent of lead.

A particularly Suitable apparatus for use in the prac tice of the inventi0n is illl]strated in the Single figure 0f the acc0Inpanying drawing. I`his apparatus comprises a cylindrical vessel 10, preferably of mild Steel, Wound with an electrical heating coil ll, and provided vvith Suitable insulation lz The vessel 10 is provided with a hermetically sealed top Or cover 13, )ierced by a conduit 14 through Which the molten an0y, or replacement magnesium nletal, may be intr0duced into the vessel 10. The 0uter end of the conduit 14 is normany closed by a detachable cover 15- A Inild steel tube 16 is suitably Suspended Within the vessel 10 by means (not Shovvn) vvith its open b0ttom end spaced fr0m the botton1 0f the vesse1 and its open top end Spaced from the top Of the vessel, the lovver end, ortion 21, 0f the tube 16 being slightly enlarged. A mild Steel tube l7, Supported by the cover 13 by Ineans (not shovvn), extends through the cover 13 int0 the vessel 10 and surrounds the tube l vvith itS 10Wer open end be10vv the upper end of the tube 16 to provide an annular )as- Sage therebetvveen The upper end Of the tube 17 is cl0sed by a cover 18 Secured theret0 by nleans (not Shown). A conduit z0 for introducing cyclopentadiene int0 the vessel 10 extends through the c0ver 18 0f the tube 17 and into the tube l vvith its lower end slightly above the lovver end 0f the tube 16, the conduit zo being Suita bly supp0rted by means (not Shovv1) to provide an annular passage 19 between its outer surface and the inner Surface of the tube 16. Preferably, the conduit 20 is provided With al1 enlarged Sl0tted lower end, portion 23- The upper end of the conduit 20 c0mmunicates with a Source (not Shown) of cyc10pentadiene under pressure A conduit 24 rovides c0mmunication between the interior of the tube 17 and a suitable condenser (n0t shown for condensing gaseous dicyc10pentadieny1n1agnesium to liquid or S01id In operation of the apparatus, molten nlagnesium alloy iS introduced int0 the vessel 10 t0 a level indicated at 3", namely, about 18 inches ab0ve the 10Wer end of the tube 16, and the apparatus is purged vvith an inert gas Such as argon The Inolten alloy is n]aintained at a desired temperature by the heating c0ils ll (:ycl0pentadiene is introduced int0 the conduit 20 under a pressure suicient t0 0verc0me the hydraulic head of the n10lten anoy and passes int0 the passage 19 in contact vvith the IT10lten all0y. AS the cyc10pentadiene reacts vith the molten magnesium alloy in the passage 19 the gaseous dicyc10pentadieny1magnesium and hydrogen formed 0W upwardly in the passage l and separate from the molten anoy at the surface 0f the latter and then pass through the conduit 24 0 the condenser 1he upward OW of the gaseous pr0ducts callses molten metal t() 0W in an endless path upwardly in the passage 19, downwardly be tvveen the tubes 16 and 17, and thence upwafdly in the passage l If desired, 0W Of the m01ten metal may be augmented by a pump withdrawing m01ten metal from Within the vessel 10 and discharging int0 the bottom open end of the tube 1G' In a given run of 40 hours, 50 liters of liquid cyc10pentadiene (run at a n0vv fate cor- Tesponding t0 1 to 2 liters liquid cyc10pentadiene per hour) Were converted in 32 percent yield to the desired dicyclopentadieny1magnesium we claim:

1. In a Inethod f01' preparing magnesium dicyc]0- pentadieny1 Wherein cyc10pentadiene iS Teacted at an elevated temperature With magnesium t0 form magnesium dicyc10pentadieny1, the improvement wherein the cyc10pentadiene is contacted vvith a rn0lten alloy of n1ag- IlesiuIn and lead at Said elevated telT1perature at a selected p0int vvithin a confined reaction Zone while causing IT101ten alloy t0 move along an endless path passing through said oint, a portion of said path extending up Wardly fron1 Said point, Said all0y containing about 35 

